Out now: Ultima Forever is the App Store's biggest free-to-play RPG

Ultima Forever: Quest of the Avatar is available now on iOS at no cost. Touted as "the biggest RPG on the App Store," it's a spiritual successor to the role-playing game Ultima 4: Quest of the Avatar, which first released in 1985.

Forever takes players back to Britannia and resumes 21 years after the former game's events. A plague called the Black Weep is spreading across the land, and Lady British is recruiting heroes to help save the world.

EA Mobile has designed the open-world quest experience specifically for touch devices. An Android version will be available at a later date. A PC port may happen if interest is strong enough.

Forever does contain in-app purchases in the form of gold keys. It also features dungeon co-op for up to four players and hundreds of hours of content. Dungeons are short, though — about five minutes each — which should facilitate quick-play sessions.